The present invention is directed to an improved rotatable electrical connector. More particularly, the invention relates to an improved electrical connector for use with telephone cords, such as coiled telephone cords, to prevent the cord from becoming twisted and/or "knotted-up".
Numerous rotatable electrical connectors for use with telephone cords have been proposed. For example, in U.S. Pat. No. 2,414,957 a swivel connector is disclosed wherein the main body has a turning head rotatably fitted thereon via a ball raceway and bearing balls. A central current conductor in the form of a rod is employed with intermediate and outer current conductors which are of tubiform. Terminal parts are associated with each of the conductors. This known type of swivel connector is relatively bulky, requires a substantial number of components, and hence is relatively expensive to make and may also be prone to breakage and to not affording a low friction rotation which would obviate its usefulness.
More recently, a rotatable electrical connector for telephone cords is disclosed in U.S. Pat. No. 4,533,796 wherein a hollow inner cylindrical member is telescoped within a hollow outer cylindrical member with a pair of ball bearing members supporting the outer member on the inner member for rotation about a central longitudinal axis. The exterior of the outer member supports a plurality of split conductive rings spaced along the central longitudinal axis that are in alignment with respective continuous rings on the inner member. A plurality of apertures are formed in the wall of the outer member in alignment with the conductive rings, and these apertures contain spring-biased balls in rolling contact with the rings so as to maintain good electrical continuity between the innermost continuous rings and the outermost split rings. This known connector is relatively complex, it requires a substantial number of parts, is rather bulky in terms of its length, and relatively costly to make. It also may be prone to breakage and friction problems.
An object of the present invention is to provide an improved rotatable electrical connector which avoids the aforementioned disadvantages of the known rotatable electrical connectors for telephone cords and the like. More particularly, an object of the invention is to provide an improved rotatable electrical connector which is sturdy enough to withstand abuse such as pulling and impact, requires only a minimum number of parts, offers low frictional resistance to rotation, and is very compact and economical to produce.
These and other objects of the invention are attained by the provision of the rotatable electrical connector of the invention. The connector comprises first and second connector members. Means are provided for rotatably connecting the first and second connector members together for rotation with respect to each other about an axis of rotation which extends through the connector members. A plurality of concentric electrically conductive rings are provided on the first connector member about the axis of rotation in radially spaced relationship so as to face the second connector member. The second connector member is provided with a plurality of sliding electrical contacts, which are in electrical contact with respective ones of the plurality of concentric electrically conductive rings on the first member so as to remain in electrical contact with relative rotation of the first and second conductive members.
According to the disclosed, preferred embodiment of the invention, the plurality of concentric conductive rings are located in a single plane which traverses the axis of rotation. More particularly, the single plane is perpendicular to the axis of rotation. This permits the axial length of the rotatably electrical connector to be relatively small, so that the connector is compact. The sliding electrical contacts are yieldably biased in electrical contact with the respective rings.
In one form of the invention, the means for rotatably connecting the first and second connector members together comprises one of the first and second connector members being telescoped within the other. The other connector member is provided with a radially inwardly directed flange extending from an outer surface of the connector about a portion of the one connector to hold the one connector in telescoped position within the other connector member while permitting relative rotation of the first and second connector members about the axis of rotation. The flange can be coated or made from a low friction material such as Teflon, for example, to minimize sliding friction between the connector members during relative rotation. In another form of the invention, the means for rotatably connecting the first and second connector members comprises a fastener extending between the connector members along the axis of rotation. Respective parts of the fastener can be formed integrally with the connector members.
An outer end of one of the first and second connector members has a female electrical socket member and an outer end of the other connector member has a male electrical plug member. Each of the male and female members is adapted to make electrical connection with a separate set of electrical conductors. Means are provided in the connector for electrically connecting each separate conductive ring and each separate sliding electrical contact to the one of the male and female members that is on the outer end of its connector member. The sliding electrical contacts are yieldably biased against respective ones of the concentric conductive rings to maintain electrical contact during relative rotation of the first and second connector members. Standard four wire telephone connections can be made employing three concentric conductive rings and an additional electrically conductive contact located on the axis of rotation with a corresponding sliding electrical contact being provided in the second connector member in electrical contact with the additional contact in the first member. Alternatively, four concentric electrically conductive rings can be employed as with the use of a fastener extending between the connector members along the axis of rotation. Presently, a telephone uses four electrical contacts. However, the exact number of rings and their respective opposing contacts can of course be varied if future needs dictate. Other non-telephone uses of this invention may require more or less than the four contacts required for telephones.
The rotatable electrical connector of the invention is advantageously connected at one end to a telephone and at its other end to a telephone cord to prevent the cord from becoming twisted and/or "knotted-up". The connector is also useful for linking two telephone cords. The connector of the invention can also be built into the telephone as an integral part thereof or, alternatively, could be built into a wall socket. The rotatable electrical connector of the invention is simple, and expensive to make, sturdy and effective for the intended purpose.
These and other objects, features and advantages of the invention will become more apparent from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the invention.